1. Field of the Invention
The invention relates to a vehicle navigation system, and more particularly to systems having a database that stores map data and methods for estimating energy consumption of a vehicle for a link of a route.
2. Related Art
Navigation systems are used in vehicles to calculate a route from a present vehicle position to a predetermined destination using map data. Navigation systems typically calculate the fastest or the shortest route to the destination using corresponding cost factors associated with the links of the route. With the costs of energy (such as fuel, gas or electricity) continuing to rise, it is desirable to reach the destination by a route that minimizes the energy consumption.
The determination of an energy efficient route may involve the use of static parameters, such as parameters associated with a speed category or a road size, and dynamic parameters, such as the driving behaviour of the driver of the vehicle. The static and dynamic parameters may be used to indicate characteristics of a link corresponding to a road segment. Although the use of these parameters may provide a good approximation of the energy consumption for a given route, it would be desirable to further improve the accuracy with which energy consumption is estimated.
Advanced driver assistance systems (ADAS) may also be used to provide assistance to the driver of the vehicle. ADAS systems acquire information about the current driving situation or the vehicle's surroundings using sensors. The information is evaluated in order to control various systems or components of the vehicle (such as for example the electronic stability program, or ESP, and the anti-lock brake system, or ABS) or to provide feedback to the driver. Modern assistance systems may combine the use of information retrieved from sensors with static parameters obtained from a database of a navigation system. Such static parameters are generally stored in an ADAS attribute layer of the navigation database. This layer generally corresponds to the lowest map data layer (layer 13), which includes the data generally associated with the shape points of links provided at the lowest layer. In order to retrieve this data, additional access to the ADAS layer is required, resulting in slow access times. The data is associated with shape points and used for a higher level route determination, which uses higher layer links. The use of the ADAS layer data for navigation purposes is thus generally difficult and costly in terms of computing time and computing power. Accordingly, the use of the ADAS layer data for route determination in a navigation system is at least associated with a number of drawbacks.
Accordingly, there is a need for improvements in the determination of an energy efficient route.